Localizing signatures of catastrophic failure (LOCAT)

Complex materials, like ceramics, rocks and the Earth's crust, often break in a catastrophic manner, after a long period of sustained or fluctuating stress. Similar catastrophic failure events also happen in biological and social systems, as mass extinctions, tipping points, and stock market crashes, and a range of tools have been developed to address these under the general framework of 'complexity science'. Here we will use these tools to look for patterns of behaviour, and their underlying causes, in the transition from the relatively stable phase of stressing a composite natural or synthetic material to its ultimate failure. We will focus on disordered porous media such as natural rocks and combine characterization using high-resolution C-T scanning with numerical modelling of the deformation and failure process, and analysis of laboratory and natural data on deformation up to the geophysical scale, in order to address the following questions.I. What role does localisation of deformation play in global acceleration to failure?II. What is the predictability of the acceleration phase in statistical terms?III. Are there any universal signatures of the spatio-temporal evolution of damage which permit lifetime estimates for single samples?IV. What are the scaling relations that link simulations and laboratory tests to the geophysical scale.

(a) Who will benefit? - Complexity Scientists engaged in analysing and predicting catastrophic global failure events that nucleate locally. - Engineers interested in the structural strength and integrity of structures, e.g. beams and bridges, whose lifetime might be extended by non-destructive testing monitoring. - Geoscientists interested in the effect of localising signatures and spatio-temporal clustering on time-dependent hazard calculation. - Material scientists interested in using state of the art characterisation techniques such as high-resolution CT imaging as input into more accurate numerical models of porous media and their deformation. The commercial private sector will benefit by protocols being developed to use and interpret remotely sensed monitoring data in engineering structures and in the subsurface. Insurance companies, especially those interested in Catastrophe bonds, will benefit from a better understanding of the physical processes behind such events. Public sector beneficiaries will include those responsible for monitoring of natural hazards or for issuing alerts, such as avalanche warnings, slope stability assessment, or changes in volcanic and earthquake hazard due to seismic and surface deformation activity. The wider public will benefit in time from an understanding of the predictability or otherwise of catastrophic failure events - are they 'acts of god' or something that can realistically be forecast, albeit perhaps with a low degree of predictability? (b) How will they benefit? Active researchers in the disciplines above will be provided with a better understanding of catastrophic localising processes on a variety of scales in natural and man-made materials and conditions. Our scientific results will be communicated to as wide an audience as possible, to ensure effective knowledge transfer and broad impact. Engineering companies increasingly use passive monitoring of acoustic or microseismic data in operations, for example to assess the integrity of suspension bridges and of masonry beams. In oil and gas extraction downhole measurements of micro-earthquake location, strain change and orientation can now be routinely made and compared with our model predictions. Commercial companies, such as the Insurance industry, model catastrophes and their impact. Our research is at the upstream end of this process, but may prove useful in time-dependent hazard calculations due to source effects that may in time impact on re-insurance premiums. The UK hosts several relevant engineering and commercial companies, with which the PIs have direct contacts. These include including Schlumberger (at Cambridge and Bracknell), Reservoir Rocktalk, Altcom, all of whom use microseismic data to infer subsurface deformation, The UK hosts several such companies, with which the PIs have direct contacts, including Holroyd Instruments (Matlock) who speciliase in NDT monitoring of bridges, Schlumberger (at Cambridge) who use microseismic data to infer subsurface deformation, and Risk Management Solutions (London) who specialise in the 'Cat bond' re-insurance market. Ongoing involvement with these economic end-users will occur throughout the project to minimise the time to any application. The results will be of immediate interest to the non-destructive testing community, to microseismic companies, and to public authorities engaged in hazard warning. To effect these we will develop suitable metrics of localisation and protocols for estimating hazard and risk to integrity. Staff will acquire skills in computational modelling, data analysis, including statistics, and in the public communication of science, included in the University of Edinburgh FEC costs as training blocks available free to all research staff.